Monitoring of humpback chub, bluehead sucker, and flannelmouth sucker in the Little Colorado River, Grand Canyon, Arizona

Authors: David R. Van Haverbeke, Michael J. Pillow, Dennis M. Stone, Kirk L. Young

Year: 2013 (xlv)

Abstract

Since 2000, a series of two-pass, closed mark-recapture efforts have been conducted in the spring and in the fall in the Little Colorado River to track the abundance of humpback chub, Gila cypha. During spring 2013 the estimated abundance of humpback chub ¡Á150 mm in the lower 13.57 km of the Little Colorado River was 8,549 (SE = 757). Of these fish, it was estimated that 5,734 (SE = 512) were ¡Á200 mm. These numbers indicate that the spring spawning abundances of humpback chub have remained relatively stable or have continued to increase since experiencing significant post-2006 increases. A similar pattern has been seen during the fall. In addition, bluehead sucker, Catostomus discobolus, and flannelmouth sucker, Catostomus latipinnis, underwent significant post-2006 increases in relative abundance during the spring season, but have since declined. These results suggest that sometime during the mid-2000s, conditions were favorable for all three large bodied native fishes in Grand Canyon. These favorable conditions are thought to be related to warmer water temperatures experienced in the Colorado River because of drought and a system-wide decline of non-native salmonids in the Colorado River. In addition, it is thought that benefit has accrued to humpback chub because of translocation efforts within the Little Colorado River.